Vertical turbine pumps are commonly used in a variety of industries to pump water or other fluids from a source below ground level, such as a well or sump. Another common application of vertical turbine pumps is in a pressure boosting configuration in a pipeline. Typical industries in which vertical turbine pumps are used include agriculture, water/wastewater, industrial, oil & gas and mining.
Vertical turbine pumps may be structured and configured in a number of ways. In general, however, vertical turbine pumps comprise a drive shaft which, in operation of the pump, is oriented in a vertical direction to operatively rotate at least one impeller. A drive motor is typically located at the upper end of the vertically-oriented drive shaft, and the impeller or impellers are positioned at the opposing end of the vertical drive shaft. An impeller of the pump may typically be housed in a structure known in the industry as a bowl, and a vertical turbine pump having a number of impellers will be configured with a series of bowls in an assembly, each bowl housing an impeller.
In operation, the vertical turbine pump is vertically oriented with the bowl assembly positioned in a sump, well or barrel and the motor or drive means is located above ground. The rotation of the impeller or impellers moves fluid upwardly through vertically-oriented piping to an outlet or discharge that it positioned either above ground or below ground, depending on the application requirements. In certain applications, the vertical turbine pump may be oriented at an angle from the vertical direction.
Vertical turbine pumps further include bearings which surround and support the drive shaft in its rotation. Bearings are located in variable positions along the drive shaft of vertical turbine pumps, including between the drive shaft and the bowl or pump casing, at the suction bell, at column lineshafts and at seal housings near the drive motor. The bearings must be lubricated to maintain optimal operation of the bearing as the drive shaft rotates within the bearing. One common means of lubricating the bearings in a vertical turbine pump is to employ as the lubricant the fluid being pumped, thereby avoiding the use of oil or grease as the lubricating agent. This is accomplished by directing the high pressure pumping fluid into the bearings by venting means. An example of such means is described in U.S. Pat. No. 5,147,179, which discloses a cascaded venting system for providing pumping fluid as the lubricant to a series of pumping section bearings in a multistage pump.
While lubrication systems of the type described in the prior art are satisfactory for use in pumping applications where the fluid being pumped is clear liquid or liquid with very low solids content, these systems are problematic in applications where the fluid being pumped contains solids or particulate matter. The solids in the pumping fluid are abrasive and cause a wearing of the adjacent surfaces of and between the rotating drive shaft and the bearing. The degradation of the bearings results in reduced pumping efficiency and excessive vibration, and the pump must eventually be taken out of service for significant repair.
In other known pump systems, a clean fluid flushing system is used to flush the bearings to eliminate solids at the bearing surfaces. However, such clean fluid flushing systems are not always available given certain factors like pumping location. Furthermore, the use of clean flushing fluid can add significant operational costs. Enclosed lineshaft bearings comprising an enclosed tube are also used to isolate lineshaft bearings, and a clean fluid flushing system is used to lubricate the bearing. However, such enclosed lineshaft bearing systems, while useful for the lineshaft, cannot be used for bowl or pump casing bearings.
Thus, new means for providing extended bearing life in vertical turbine pumps, particularly when used in the processing of slurries or under other abrasive conditions, is needed.